Search

Trans fatty acids occur in food either naturally or produced during heat processing of food containing unsaturated fats. Naturally occurring trans fatty acids have different physiological and biological functions as compared to those formed in heat processed food which increase the risk of coronary heart disease. The aim of this study was to investigate the effect of heat treatments [heating temperature: 120, 150, 190 and 250°C and heating period: 10, 30, 60 and 180 minutes] on the amount of trans fatty acids (as elaidic acid) of fat and oil samples [two solid-state (margarine and ghee) and two liquids-state (olive oil and corn oil)]. Results showed that elaidic acid content in margarine was not affected by heat at 120°C at all studied heating durations. At 150, 190 and 250°C, there is a cubic significant relationship between elaidic acid content and time of heating. Elaidic acid content in ghee was not affected by heat treatment at 120°C, while at 150°C, there was a cubic significant relationship between elaidic acid content and heating time. At 190°C, there was a negative linear relationship between elaidic acid content and time of frying, while at 250°C, there was oscillatory relationship in the amounts of elaidic acid with time of heating. As a conclusion, all margarine and ghee samples analyzed in this study had elaidic acid before and after heat treatment used in the study. However, corn oil and olive oil were free from elaidic acid before and after studied heat treatments. Therefore, it is recommended to cook and bake with vegetable oils (such as corn oil) instead of solid fats, and to keep margarine and ghee consumption as low as possible in nutrition.

The quality of extra virgin olive oil (EVOO) is intimately affected by packaging material and storage temperature. In this study, the influence of packaging materials and elevated temperature on EVOO quality was investigated during six months. At ambient temperatures, oil maintained EVOO when stored in glass, polyethylene terephthalate (PET), high density polyethylene (HDPE), cans and Pottery in terms of chemical tests (acidity, peroxide value, K232, and K270). Loss of phenols was the highest in pottery-stored oil and the lowest was found in glass-stored oil. Only PET-stored oil maintained the EVOO grade in terms of sensory evaluation when stored at room temperature. At elevated temperature, oil stored in all packaging materials lost extra virgin quality in terms of chemical tests. The loss of phenols was the largest in HDPE and smallest in cans-stored oil. Sensory evaluation, maintained glass-stored oil and PET-stored oil as EVOO. This study has reaffirmed that at both storage temperatures, the best container in maintaining the EVOO quality was glass and the worst was pottery. Grading of stored olive oil under investigation using sensory evaluation solely was not sufficient. Also it was clear that the absorption coefficient K270 was the most sensitive determinant chemical test that determines the quality of stored olive oil and could be used as a rapid indicator test.